The PHQ-9 (PHQ-D in some sources) is the 9-question depression scale from the Patient Health Questionnaire (PHQ). The results of the PHQ-9 may be used to make a depression diagnosis according to DSM-IV criteria. (see: Wikipedia)

scoring_phq9(data, items = 1:9, keep = TRUE, nvalid = 6, digits = NULL)

Arguments

data

a data.frame containing the PHQ-9 items orderd from 1 to 9. The data.frame may contain further variables.

items

A character vector with the PHQ-9 item names ordered from 1 to 9, or a numeric vector indicating the column numbers of the PHQ-9 items in data.

keep

Logical, whether to keep the single items and whether to return variables containing the number of non-missing items on each scale for each respondent. The default is TRUE.

nvalid

A numeric value indicating the number of non-missing items required for score calculations. The default is 7.

digits

Integer of length one: value to round to. No rounding by default.

Value

The function returns 3 variables:

  • nvalid.phq9: Number of valid values (MAX=9)

  • score.phq9: PHQ-9 score

  • cutoff.phq9: PHQ-9 as categorical variable

Details

  • Number of items: 9

  • Item range: 0 to 3

  • Reverse items: none

  • Score range: 0 to 27

  • Cut-off-values: < 5 = "minimal"; 5 to 9 = "mild"; 10 to 15 = "moderate"; 15 to 19 = "moderately severe", \(\ge\) 20 = "severe"

  • Minimal clinically important difference: none

  • Treatment of missing values: Questionnaires with up to two missing values are scored, replacing any missing values with the average score of the completed items. (Arrietta et al. 2017)

References

Arrieta et al. (2017) (https://doi.org/10.1002/jclp.22390)

Kroenke et al. (2010) (https://doi.org/10.1016/j.genhosppsych.2010.03.006)

Examples

if (FALSE) { library(dplyr) items.phq9 <- paste0("phq_", seq(1, 9, 1)) scoring_phq9(mydata, items = items.phq9) }